Pipe calipers



June 4, 1957 J. c. KINLEY 2,794,260

PIPE CALIPERS Filed June 27, 1955 2 Sheets-Sheet 1 A TTR/VEKS June 4, 1957 J. c. KINLEY 2,794,260

PIPE CALIPERS United States Patent() PIPE CALIPERS John C. Kinley, Houston, Terr. Application June 27, 1955, Serial No. 518,005 12 Claims. (Cl. 33-178) This invention relates to new and useful improvements in pipe calipers.

An object of this invention is to provide a new and improved pipe caliper or calipering tool for obtaining an indication of surface variations on the inside of a pipe, wherein means are provided for determining the point in the pipe at which the indicating or recording of said surface irregularities is commenced.

An important object of this invention is to provide a new and improved pipe caliper or calipering tool for obtaining an indication of surface variations on the inside of a pipe, wherein the actuation of said tool is controlled by a timing mechanism.

Another object of this invention is to provide a new and improved tool for obtaining an indication of surface variations in a pipe, wherein the tool has a timing means for regulating the release of the means for driving the recorder mechanism of the tool, whereby the driving of the recorder mechanism is regulated by said timing means.

Another object of this invention is to provide a new and improved tool for obtaining an indication of surface variations in a pipe, wherein said tool has a timing means for regulating the release of the feelers or contact members of the tool to thereby begin the calipering of the inside of the pipe with said feelers.

A further object of this invention is to provide a new and improved pipe caliper or calipering tool having means for locking the feelers and the recorder mechanism of the tool and also having means for releasing the locking means to permit the feelers and the recorder mechanism to start `their calipering and recording functions.

The construction designed to carry out the invention will be hereinafter described, together with other features thereof.

The invention will be more readily understood from a reading of the following spec`cation and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown, and where- Figure l `is a view, partly in elevation and partly in section, illustrating the tool of this invention.

Figures 2A, 2B and 2C are views, partly in. elevation and partly in section, illustrating the upper, middle and lower portions, respectively, of the caliper or calipering tool of this invention.

Figure 3 is a view, partly in elevation and partly in section, illustrating a part of the upper portion of the tool of this invention illustrated in Figure Figure 2A in that the locking mechanism is illustrated in the locked position in Figure 3 as compared to the unlocked position in Figure 2A.

Figure 4 is a horizontal sectional view taken on line 4-4 of Figure 3.

Figure 5 is a view, partly in elevation and partly in section, illustrating a modied form of the caliper or tool of this invention.

ln the drawings, the letter T designates generally the 2A, but differing from this invention.

Patented June 4, 1957 caliper or calipering tool of this invention which is adapted to be positioned in a pipe P such as a well pipe or tub ing which, in the usual case, is disposed within a well casing C. The tool T is supported by a flexible support or wire line 10 which extends to the surface of the well so that the tool T is adapted to be lowered to the point in the pipe P at which it is desired to begin making the record 'of the surface variations in the pipe P. Ordinarily, for making such record or indication of the surface conditions or variations in the pipe P, the tool T is raised or pulled upwardly in the pipe P by raising the exible wire line 10. The caliper or tool T of this invention includes a mechanism for determining or regulating the time at which the caliper or tool T begins to indicate or record the surface Variations or conditions on the inside of the pipe P, as will be explained. Thus, the caliper or tool T of this invention can be maintained in an inactive condition as it is lowered into the pipe P to the predetermined point at which it is desired to begin the calipering operations. The timing mechanism will prevent the activation 0f the caliper or tool to make a record of the surface conditions until the tool has reached the predetermined point for the beginning of the calipering or recording operation. Once the timing mechanism does render the tool T active for indicating or recording the surface conditions on the inside of the pipe, then the tool T can be raised on the flexible line 10 in the usual manner to obtain the usual record or indication.

The details of the complete, or substantially complete, caliper or calipering tool T of this invention are shown in Figures 2A, 2B, and 2C. The lower portion of the tool T may take numerous forms, but preferably such lower portion is constructed as illustrated and described in the copending U. S. patent application, Serial No. 432,764, which was tiled May 27, 1954, in the names of Myron M. Kinley and Frank F. Robertson. As illustrated in the drawings, such lower portion of the caliper or tool T includes an outer housing or body 11 which is substantially cylindrical in construction and which extends from the lower end of the tool T to the upper end thereof for connection with the flexible line 10 (Figure 1). Such body 11, as illustrated, is preferably formed of a plurality of sections for convenience of assembly. A plurality of circumferentially-disposed contact members or feelers 12 are mounted on the body for pivotal movement relative thereto, with springs or resilient members 14 also being mounted on the body or housing 11 for urging the feelers 12 outwardly into engagement with the inside surface of the well pipe or tubing P. The feelers 12 pivot inwardly and outwardly in response to the surface variations or irregularities in the inner surface of the pipe P and the upper ends of the feelers 12 are adapted to contact a cone or transmitting member 15 so that the pivotal movement of the feelers 12 is transmitted into longitudinal movement of the cone or transmitting member 15. Such movements of the cone 15 are indicated or recorded in the usual manner for calipering tools andas illustrated in the drawings, a rod 16 extends upwardly from the cone 15 and has connected thereto a rod 17, a pivoted bell crank arm 18 which is adapted to pivot about the screw 19, and a stylus or recorder member 20, which stylus 20 traces or marks a line L on a tape or recording chart 21.

The chart or tape 21 is moved longitudinally relative to the stylus 20 by means of any suitable driving mecha-V As illustrated in the drawings hereof, the

tapeor chart 21 is wound from the reel 22 to the take-up reel 23 by rotating the reel 23 through the gears y24. For driving the gears 24, a drive wheel 25 (Figure 2A) is provided which has a knurled or roughened outer circumferential surface which is adapted to contactthe innerfsurface ofthe pipe P so thatsuchdrive wheel 25 is rotated upon a longitudinal movement 'of the-tool T within the pipe lP. The drive .wheel 25 is supported in the housing or `body 1.1 and projects through an opening or slot 11a of the body 11. The drive wheel .25 .rotates about Aa shaft 26 which is mounted on .a support .ann 27 which has its lower end pivotallyconnected at 28 to the body or housing .11. A coil spring 30 normally urges the drive wheel /25-.outwardly=through the slot 11a so as to vmaintainAthe-knurled -surface of the drive wheel 25 in contactwith the inside `surface Vof `the pipe P. A `stop 31 limits the extent of the outward movement .of the drive wheel`25. The shaft 26 upon which the wheel 25 is mounted .is `providedwith -a bevel Agear 32 -in mesh with a companion bevel -gear '33 secured'to la exible shaft 34 which, in turn, Iis connected by coupling 35 to a rotating shaft '36 extending through la gland 37. The shaft 36 is coupled through a coupling connection 40 to a shaft 41 lwhich yhas a worm gear -42 connected `therewith for driving Vthe series of -gears 24. Thus, the rotation of the drive wheel 25 upon a .longitudinal -movement ofthe tool T in-the pipe P Aeffects alturning of the reel 23 which causes the chart 21 to move -longitudinally relative to the-stylus 20.

In order to prevent the `making of a record -on the chart 21 prior to the time that the tool T has vbeen lowered Ato the desired depth in the pipe 4or tubing -P, the caliper or tool T of this invention has been provided with .a mechanism for locking the drive wheel in an inactive position and subsequently releasing same to its active position after a predetermined period of time. As best seen in Figure 3, the arm 27 has an upper extension 27a which is Acontacted by a lock pin or rod 40 so as to hold the arm 27 in a retracted position and to prevent the spring 30 `from urging the arm 27 and the drive wheel 25 outwardly so as to cause `the wheel 25 to contact .the pipe P. Thus, so long as the pin 40 is in engagement .with the upper portion 27a of the arm 27, the drive wheel 25 cannot move into contact with lthe inside of the pipe P and therefore the drive wheel 25 is in an inactive position since it cannot be driven by the longi tudinal movement of the tool or caliper T.

The lock pin 40 extends through an opening 41a in a lateral support plate 41 which is welded or .otherwise secured to the inside of the housing or body 11. The rod 40 has a laterally extending ring or plate 42 which is welded or otherwise secured to the rod 40 and which is positioned above 4the plate 41. A spring 43 is conned between the plate 41 .and the plate 42 so Aas yto constantly urge ythe lock pin or rod 44B upwardly, which upward movement is normally prevented by reason of the .Contact of the upper vend of the rod or pin 4.0 with the lower surface of a disk or plate 44 which is mounted on a shaft 45 of a power clock 46. The clock 46 is of any .known construction which is adapted to be set for imparting rotation to the shaft 45 and the disk 44. The clock 46 may be wound manually or by any suitable electric device (not shown). Preferably the clock 46 is supported on a plate 47 which is welded or otherwise secured to the housing 11, and the outer end of the shaft 45 is supported in suitable bearings 4S disposed in another support plate 50 which in turn is welded or otherwise `secured to the inside of the housing 11. It will be noted that the upper portion of the rod or .pin 40 extends through an opening 50a in the plate 50 and is slidable relative thereto. The plate 44 has an opening or notch 44a formed therein which Vis of sufficient size to permit the rod 40 vto pass therethrough when the opening 44a is aligned with the rod 40. However, so long as'the opening or notch 44a in the disk or plate 44 is -notaligned with the `lock pin or rod 40, the pin vor rod 40 is in the locking position to hold the wheel 25 in its inactive position. The notch or opening u44a is, of course, moved into alignment with the upper end of the rod 40 by a rotation of the plate or disk 44 with the power clock 46. The distance that the notch 44a must travel prior to the alignment with the rod 40, of course, determines the length of time before the rod 46 is released from its locking position. Thus, if it is desired to maintain the drive wheel in an inactive position for a suliicient length of time to lower the tool T to a predetermined depth in the pipe P, the disk 44 is set so that the notch or opening 44a is a distance from the rod 40 to require a lapse of enough time to permit the tool T to reach such predetermined depth before the notch 44a is aligned with the rod 40 for receiving same.

If desired, the feelers or contact members 12 may also be locked against outward movement into contact with the inside surface of the pipe P until it is desired to begin the recording or indicatingv peration for making a record of the inside surface of the pipe P. For such purpose, a locking device R (Figure 2B) may be provided. The device R includes a laterally extending shaft 60 mounted between plates 61 and 62 for pivotal movement relative thereto. A clevis 63 is wel-ded yto the shaft 36, and it carries a pin 63a on which is mounted a cylindrical roller 64 which engages the upper end ofthe longitudinally movable rod 16 when the locking device R is in the locking position to maintain the cone or transmitting member l-15 in a lower position, whereby the feelers or contact members 12 are maintained retracted or pivoted inwardly. It will be evident that when the feelers or contact .members 12 are held inwardly, .they cannot contact the inside surface of the pipe P. A coil spring 65, -or any other similar resilient means, urges the shaft 60 to pivot or turn so as to swing the clevis 63 and roller 64 upwardly to a released position, but during the lowering of the caliper tool T in the pipe P, su-ch spring 65 is prevented from releasing the roller 64 from its seated position on the upper end of the rod 16 by reason of the engagement of a lug 66 on the shaft 6i) with a latching arm 67, which extends laterally through a longitudinal opening 62a in the plate 62 and has connection with a release rod 70 extending upwardly between the plate 62 and the body or housing 11. The rod 70 extends upwardly to a lateral arm 71 which is welded or otherwise secured to the lock pin or rod 40. Thus, movements ot the lock pin or rod 40 are transmitted to the rod 70 by reason of the connecting arm 71 and such movements of the rod 70 are transmitted to the latch arm 67. Therefore, upon a release of the lock pin 40 from the upper n'rtien 27a `of the arm 27 by the movement of the rod 40 into the notch or opening 44a, the upward movement of such rod or pin 4t) effects a similar upward movement of the latch arm 67, whereby the engagement thereof With the lug 66 is released to permit the spring 65 to thereafter swing the shaft 6) to position the roller 64 to one side of the shaft 16 whereby the shaft 16 can thereafter move longitudinally within limits without contacting the roller 64 or any other part of the lock device R. It should be noted that in Figure 2B, the latch arm 67 has already been released, but normally during the running-in of the tool T, the latch arm 67 would be behind the lug 66 to prevent the rotation of the shaft '60 by the spring action of the coil spring 65.

In the operation or use of the caliper or tool T of this invention, the clock 46 is wound or otherwise set when the Atool T is at the surface of the well in which the pipe' P is located. Suitable means is, of course, provided for access to the interior of the housing 11 `for such setting of the clock 46. The plate 44 is also set so that the notch or opening 44a is positioned a suicient distance from .the lock pin or rod 40 to require a certain length of time before the alignment of the pin 40 with the opening 44a occurs. In other words, the clock 46 .is conare-ined ory turns the plate or disk 44 at a predetermined rate. Such rate can readily be calibrated so that the' proper setting of the notch 44a with respect to the lock pin 40 is obtained prior to the lowering of the tool T into the well pipe P.

With the clock 46 and the plate 44 thus set, and with the pin 40 in its locking position so as to hold the wheel 25 in an inactive position (Figure 3), and with the lock device R in its locking position with the latch 67 behind the lug 66, the tool T is lowered into the well pipe P on the exible line 10. The clock 46 and the plate 44 are set so that the locking pin or rod 40 is released when the tool T has reached the lowermost point of the portion of the pipe P which is to be calipered. Thus, as the tool T is being lowered in the pipe P, the clock 46 is gradually turning the plate 44 so as to move the notch or opening 44a into alignment with the upper end of the rod or pin 40, and such alignment occurs when the tool T has reached the lowermost point of the portion of the pipe P to be calipered. Of course, the time at which the lock pin or rod 40 is released can be delayed to some extent so as to be certain the pin 40 is not released prior to the time that the tool reaches the lowermost point of the portion of pipe to be calipered, but in any event, the tool is permitted to reach such lowermost point before the drive wheel 25 begins its driving action. Thus, when the opening or notch 44a becomes aligned with the rod 40, the spring 43 acts against the plate or ring 42 to urge the rod 40 upwardly so as to move the lower end of the rod 40 above the upper portion 27a of the arm 27 (Figure 2A). The clock 46 is stopped by reason of the projection of the upper portion of the rod 40 into the notch or opening 44a, unless a suitable clutch (not shown) is shown. Once the rod 40 is moved upwardly by reason of the alignment with the notch or opening 44a, the spring 30 acts to move the arm 27 about its pivot 28 so as to move the drive wheel 25 into contact with the inside surface of the pipe P. Thereafter, longitudinal movement of the caliper or tool T effects a rotation of the drive wheel 25.

In addition to the releasing of the lock pin 40 so as to move the drive wheel 25 into driving engagement with the pipe P, the rod 70 is also moved upwardly so as to disengage the latch arm 67 from the lug 66 whereupon the spring 65 acts to swing or pivot the shaft 60 and the roller 64 away from the upper end of the rod 16. Thereafter, movements of the feelers 12 are transmitted to the. cone or transmitting member 15 and the shaft 16 so as to effect a pivoting action of the crank arm 18 for producing the lateral deections in the line L in accordance with the surface variations or conditions in the pipe P, as more fully explained in said copending application, Serial No. 432,764.

It should be noted that the locking not be essential to prevent the making of a record or indication of the feeler movement during the lowering of the tool T into the well pipe P, since no record would be obtained so long as the drive wheel 25 is maintained out of engagement with the inside of the pipe P by the lock pin 4t). Therefore, it can be appreciated that the locking device R could be eliminated and only the mechanism for locking the drive wheel 25 could be utilized, if desired. The making of the actual line L or record is, of course, obtained in the usual manner once the wheel 25 and the feelers 12 are in their active positions in contact with the inside surface of pipe P. The record is `obtained as the tool or caliper T is raised upwardly in the pipe P on the flexible line 10.

In Figure 5, a mechanism is illustrated for locking the feelers or -contact members 12, which mechanism is substantially the same as illustrated in Figures 2A and 3 for maintaining the drive wheel 25 in a retracted position. As shown in Figure 5, the locking device R of Figure 2B is eliminated and instead, a clock 146 which is a power clock ofV a known type such as is described above inVr structed so that it rotates device R would 6 2A and 3 is mounted on a plate 61 and 62. The power clock which has attached thereto by means, a disk or plate 144 connection with Figures 147 between the plates 146 drives a shaft 145 welding, or any other suitable which has a notch or opening (not shown) therethrough similar to the notch or opening 44a illustrated in Figure 4.v The shaft preferably turns in a bearing 148 mounted in a plate which is weldedor otherwise secured betweenthe plates 61 and 62. `A lock pin 0r rod 140 is slidably Adisposed in openings of the plate 150 and the lower plate 141, which is also welded or otherwise secured to the plates constantly urged upwardly by a spring 143 vwhich is conned between the plate 141 and a ring or plate 142 which is welded or otherwise secured to the rod 140. The lower end of the rod 140 contacts the lateral portion 16a of the rod 16 so that when the upper end of the rod 140 is in contact with the lower surface of the disk or plate 144, the rod 16 is prevented from moving longitudinally in the housing 11. However, upon the alignment of the pin 140 with the opening or notch in the plate or disk 144, the spring that opening a suicient out of the Way of the rod 16, whereby the rod 16 is thereafter free to move longitudinally in accordance with the longitudinal movements of the cone 15 which are transmitted from the movement of the feelers. Such movements of the rod 16 are of course transmitted to the rod 17. The rod 17 of Fig. 5 is identical with the rod 17 of Fig. 2B and it connects with the recording structure of Figs. 2B and 2A in the same manner as described previously in connection with such figures.

ln the operation or use of the modification illustrated in Figure 5, the clock 146 and the plate 144 are set in ther same manner as described above for the clock 46 and the plate 44 so that the notch or opening in the plate 144 is positioned a sufficient distance from the rod 140 to require a predetermined length of time before the alignment with the rod 14). Thus, the feelers 12 are maintained in a locked position for a predetermined length of time, which time is ordinarily that time required to lower the tool T to the lowermost point in the pipe P at which it is desired to begin calipering the pipe P. VThe form of the device illustrated in Figure 5 could, of course, be used in conjunction with the timing mechanism illustrated in Figures 2A and 3, except that the rod 70 and the arm '71 would be unnecessary since the locking device R would not be used. clocks 46 and 146 would ordinarily be set to release the lock pins 40 and 140 at substantially the same time. It will also be appreciated that the modification of Figure 5 could be utilized without any means for holding the drive wheel 25 in an inactive position out of contact with the well pipe P, since the movement of the drive wheel 25 would simply move the tape or chart 21 and would not give any record of the surface conditions or variations inside the pipe until the feelers 12 are actually released to an active position.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is:

l. In a tool for obtaining ations in a pipe, wherein said tool includes a housing,v

the housing and projecting therefeelers mounted within from for movement responsive to the variations in the inside surface of said pipe, and a recorder mechanism in4 ing, and a timing means in said housing for effecting a release of said lock means after a'predetermined time to 61 and 62.- The rod 140'is 143 moves the rod 140 upwardly through' distance to move the rod 140 In such case the powerV a record of the surface varilock means in said housingy ing, :and a timing means in said housing thereby -permit the recorder mechanism to zfunction to record -the surface variations on the insidesurface of said ipe- p .2. ,Ina tool .forvobtaining a record of the surface vvariations Ain a pipe, wherein said tool includes a housing, feelers mounted Within the housing and projecting -therefrom for movement responsive to the variations in the .inside surface `of said pipe, .and a recorder mechanism in said housing for recording the movement of said feelers, the Yimprovement residing in, lock means `in said housing for preventing .said recorder mechanism from functionfor effecting a release of said lock means after apredetermined time to thereby `permit therecorder mechanism to function yto record the surface variations on .the inside surface of said pipe, ,said timing means including a Ypower clock, and means turned by said clock for 'effecting the release of said lock means.

3. In a tool for obtaining a record of the surface variations in Aa gpipe, wherein said tool includes a housing, feelers -mounted lwithin the housing and .projecting'therefrom for :movement responsive to the variations in the inside :surface of said pipe, and a recorder mechanism in said thousing vfor recording the movement of said feelers, and a drive means for driving said recorder mechanism, :the improvement residing in, a lock means for holdin g .said idrive means in an inactive position to thereby prevent the recorder mechanism from functioning, and a timing ymeans in said housing for effecting a release of said lock means after a ypredetermined time to thereby permit the recorder mechanism to function to record the surface variations .on the inside surface of said pipe.

`4. ,Thestructure set forth in claim 3, wherein said lock means includes a lock pin in engagement with said drive means to hold same in its inactive position, and resilient means constantly urging said lock pin to a position out of engagement with said drive 4means to release said drive means toits active position, and means operable by said timing means for holding said lock pin against movement out of engagement with said drive means until a predetermined period of time has elapsed.

5. A calipering tool for obtaining an indication as to the surface variations in a pipe, comprising a body adapted to :be positioned in said pipe for movement relative thereto, ya plurality of contact members mounted on said body for .movement therewith, said contact members being movable relative to the body in response to surface variations encountered on the inside of said pipe to give an indication of said surface variations, lock means for locking said contact 4members in an inactive position, releasing means for yeiecting a release of said lock means, and a timing means for operating said releasing means after a predetermined period of time elapses.

6. A tool .for obtaining an indication as to the surface variations in a pipe, vcomprising .a body adapted to be positioned .in said pipe for movement relative thereto, a plurality of contact members mounted on said body for movement therewith, said contact members being movable relative `to the body in response to surface variations encountered on the inside of said pipe to give an indication of said surface variations, lock means for locking said contact members in an inactive position, spring means for resiliently urging said lock means to a released position, means for preventing said spring means from releasing said lock means, and a power clock operatively connected to said last-mentioned means to move same. to a position `at which Ysaid spring means .is effective to move said lock means to a released position, whereby said contact members are rendered active for movement in response to the surface variations of said pipe,

7. A calipering tool for obtaining an indication as to the surface variations in a pipe, comprising a body adapted to .be positioned in :said pipe for movement relative thereto, .alplurality of contact members Ymounted on said body for movement therewit said .contact members being movable relative -to the body in vresponse to surface variations encountered on .the inside lof said `pipe to givean indication of said surface variations, an indicating means for indicating .the movements lof Ythe contact members, a transmitting means for transmitting the movements lof the contact members to the indicating means, lock means for Ilocking -said transmitting means to thereby prevent transmission of any movement of vthe contact members to -said indicating means, releasing means for effecting a release-of said lock means, and a timing means for operating said reieasing means after a predetermined period of time elapses.

8. A calipering tool for obtaining an indication as to the surface variations in a pipe, comprising a body adapted to be positioned in said pipe for movement relative thereto, a plurality of contact members mounted on said body for movement therewith, said contactmembers being movable relative to the body in response to `surface variations encountered on the inside of said pipe to give an indication of said surface variations, a recorder means including a chart for making a record of the movements of said contact members, Va drive means for driving .said chart, lock means for locking both said contact members and said drive means in an inactive position to prevent the making of a record with said recorder means, and timing means for effecting a release of said lock means after apredetermined time.

9. The structure set forth in claim 8, wherein said timing means includes Va power clock, and a plate with an opening therein and operable by said clock and wherein said lock means includes a locking pin having one end thereof in engagement with said drive means to prevent actuation thereof and the other end thereof in engagement with said plate, and a resilient means normally urging said locking pin into contact with said plate, said resilient means moving said one end of said locking pin out of engagement with said drive means upon an alignment of said opening in said plate with said other end of said locking pin.

10. A calipering tool for obtaining an indication as to the surface variations in a pipe, comprising a body adapted to be positioned in said pipe for movement relative thereto, a plurality of contact members mounted on said body for movement therewith, said contact members being movable relative to the body in response to surface variations encountered on the inside of said pipe to give an indication of said surface variations, a recorder means including a chart for making a record of the movements of said contact members, a drive means for vdriving said chart, lock means for locking said drive means in an inactive position to prevent the making of a record with said recorder means, and 'timing means for eifecting a release of said lock means after -a predetermined time.

1l. The structure set forth in claim l0, wherein said timing means includes a power clock, and a plate with an yopening therein and operable by said clock and wherein said lock means includes a locking pin having one end thereof in engagement with said drive means to prevent actuation thereof and the other end thereof in engagement with said plate, and a resilient means normally urging said locking pin into contact with said plate, said resilient means moving said one end of said locking pin out of engagement with said drive means upon an alignment of said opening in said plate with said other end of said locking pin.

l2. A calipering ltool for obtaining an indication as to the surface variations in a pipe, comprising a body adapted to 4be positioned in said pipe for movement relative thereto, a plurality of contact members mountedfon said body for movement therewith, said contact members being movable relative to the body n response to surface variations encountered on the inside of said pipe to give an indication of said surface variations, a locking pin for .locking said contact vmembers in .an `inactive posi- 10 tion, a plate adapted to be engaged by said pin to mainsame so as to align said opening in said plate with said tain same in its locking position, said plate having an locking pin after a predetermined time whereby said lock opening therein into which said pin is adapted to move ing pin is released to permit the Contact members to funcfor effecting a release of said locking pin from its locktion to give the indication of said surface variations. ing position, resilient means for urging said pin into said 5 opening upon an alignment of said opening with said pin, N0 references Citedand a power clock connected to said plate for moving 

